Conventionally, in the manufacture of semiconductor devices, micro-processing by lithography using a photoresist composition has been carried out. The micro-processing is a processing method including forming a thin film of a photoresist composition on a silicon wafer, irradiating actinic rays such as ultraviolet rays through a mask pattern on which a pattern for a semiconductor device is depicted, developing it to obtain a photoresist pattern, and etching the semiconductor substrate using the photoresist pattern as a protective film. However, in recent progress in high integration of semiconductor devices, there has been a tendency that shorter wavelength actinic rays are being used, i.e., KrF excimer laser beam (248 nm) has been taking the place of i-line (365 nm). Along with this change, influences of random reflection and standing wave off a substrate have become serious problems. Accordingly, it has been widely studied to provide an anti-reflective coating between the photoresist and the substrate (Bottom Anti-Reflective Coating, BARC).
As the anti-reflective coating, inorganic anti-reflective coatings made of titanium, titanium dioxide, titanium nitride, chromium oxide, carbon or α-silicon and organic anti-reflective coatings made of a light absorbing substance and a polymer compound are known. The former requires an installation such as a vacuum deposition apparatus, a CVD (chemical vapor deposition) apparatus or a sputtering apparatus. In contrast, the latter is considered advantageous in that it requires no special installation so that many studies have been made. For example, mention may be made of the acrylic resin type anti-reflective coating having a hydroxyl group being a crosslinking reaction group and a light absorbing group in the same molecule and the novolak resin type anti-reflective coating having a hydroxyl group being a crosslinking reaction group and a light absorbing group in the same molecule (see, for example U.S. Pat. Nos. 5,919,599 and 5,693,691).
The physical properties desired for organic anti-reflective coating materials include high absorbance to light and radioactive rays, no intermixing with the photoresist layer (being insoluble in photoresist solvents), no diffusion of low molecular substances from the anti-reflective coating material into the topcoat photoresist upon coating or heat-drying, and a higher dry etching rate than the photoresist (see, for example, Tom Lynch et al., “Properties and Performance of Near UV Reflectivity Control Layers”, US, in Advances in Resist Technology and Processing XI, Omkaram Nalamasu ed., Proceedings of SPIE, 1994, Vol. 2195, p. 225-229; G. Taylor et al., “Methacrylate Resist and Antireflective Coatings for 193 nm Lithography”, US, in Microlithography 1999: in Advances in Resist Technology and Processing XVI, Will Conley ed., Proceedings of SPIE, 1999, Vol. 3678, p. 174-185; and Jim D. Meador et al., “Recent Progress in 193 nm Antireflective Coatings, US, in Microlithography 1999: in Advances in Resist Technology and Processing XVI, Will Conley ed., Proceedings of SPIE, 1999, Vol. 3678, p. 800-809).
On the other hand, in LSI pattern rule having a fineness of 0.13 μm or less, interconnection delay largely influences speed-up of LSI, it becomes difficult to promote the improvement of the performance of LSI by the present LSI process technology. Thus, one material used for reducing interconnection delay is interconnect material Cu.
A technique for replacing Al as interconnect material with Cu is Dual Damascene process (see, for example U.S. Pat. No. 6,057,239). In the process, an anti-reflective coating is applied on a substrate with a higher aspect ratio (unevenness) than the conventional substrate for which interconnect material Al is used.
Characteristic properties required for anti-reflective coating material for use in Dual Damascene process include control of coating performance of anti-reflective coating on a substrate of the periphery of hole in addition to the above-mentioned properties. In addition, when an anti-reflective coating is applied in a constant thickness, the material is required to have a high absorbance for light or radiation and a high flattening property that does not depend on unevenness on a substrate.
However, it becomes difficult to use organic material for anti-reflective coating as anti-reflective coating material for use in Dual Damascene process. Therefore, it is thought a process in which two layers of an inorganic or organic anti-reflective coating having a high absorbance for light or radiation and a gap fill material for lithography for flattening are used. The gap fill material for lithography is Gap-Filling material, that is, a filler or a flattening agent. It is known a gap fill material forming composition in which a polymer solution effective for Dual Damascene process is used (see, for example WO 02/05035). Further, a certain composition for filling is also known (see, for example JP 2002-47430 A).
In the process in which a gap fill material is used, generally, the gap fill material composition is applied on a substrate having unevenness such as hole or the like, and baked to form a gap fill material layer. Thereafter, an excess gap fill material layer is removed by etching, that is, etch-back is carried out. The etch-back provides a gap fill material layer with a desired thickness, and makes possible to provide the surface of the gap fill material layer having a high smoothness. And, a photoresist layer is formed directly on the gap fill material layer or on an anti-reflective coating layer which is previously formed on the gap fill material layer, and then a manufacture of a substrate is carried out by a lithography process.
The etch-back is generally carried out by dry etching. In this case, a substrate on which a gap fill material layer is formed is moved from a coater & developer (a coating and developing apparatus) to a dry etching apparatus, and etched backed by dry etching, thereafter the substrate is required to be returned to the coater & developer in order to form an anti-reflective coating or a photoresist layer. That is, it is required to be moved between two apparatuses, therefore lowering in production efficiency occurs and is pointed out as a disadvantage in this process.
In order to overcome these disadvantages in the prior processes, the present inventors propose a process in which etch-back of a gap fill material layer is carried out by use of an alkaline aqueous solution. This process makes possible to carry out a series of steps comprising application of a gap fill material composition, etch-back and forming of a photoresist layer with a coater & developer apparatus (a coating and developing apparatus), and therefore production efficiency is greatly improved.
Characteristic properties required for gap fill material which makes etch-back by such an alkaline aqueous solution possible, that is, for an alkali-soluble gap fill material for lithography are as follows: a substrate with a high aspect ratio (unevenness) can be flattened; a gap fill material layer has a solubility (etch-back property) moderate for an alkaline aqueous solution; a gap fill material layer after etch-back is insoluble in a solvent used for an anti-reflective coating or a photoresist composition (no intermixing with an anti-reflective coating layer or a photoresist layer causes); there is no low molecular matter diffused from a gap fill material layer to an overlaid anti-reflective coating or photoresist layer upon heat-drying; and it has a higher dry etching rate than a photoresist.
An object of the present invention is to provide a novel gap fill material forming composition for lithography which can fully satisfy these requirements. The present invention provides a novel gap fill material forming composition for lithography which is excellent in flattening property of substrates having unevenness like holes or trenches, is soluble in an alkaline aqueous solution, can be etched back with an alkaline aqueous solution, causes no intermixing with a photoresist layer, and provides an excellent resist pattern. Particularly, the present invention provides a gap fill material forming composition for lithography for use in dual damascene process for introducing interconnect material Cu (copper) which has been used for reducing interconnection delay of semiconductor devices in recent years.